全文获取类型
收费全文 | 7731篇 |
免费 | 1547篇 |
国内免费 | 949篇 |
专业分类
化学 | 5471篇 |
晶体学 | 116篇 |
力学 | 442篇 |
综合类 | 89篇 |
数学 | 859篇 |
物理学 | 3250篇 |
出版年
2024年 | 32篇 |
2023年 | 241篇 |
2022年 | 385篇 |
2021年 | 382篇 |
2020年 | 452篇 |
2019年 | 424篇 |
2018年 | 350篇 |
2017年 | 325篇 |
2016年 | 440篇 |
2015年 | 451篇 |
2014年 | 476篇 |
2013年 | 648篇 |
2012年 | 719篇 |
2011年 | 704篇 |
2010年 | 507篇 |
2009年 | 469篇 |
2008年 | 444篇 |
2007年 | 395篇 |
2006年 | 327篇 |
2005年 | 300篇 |
2004年 | 249篇 |
2003年 | 205篇 |
2002年 | 181篇 |
2001年 | 154篇 |
2000年 | 111篇 |
1999年 | 137篇 |
1998年 | 105篇 |
1997年 | 90篇 |
1996年 | 91篇 |
1995年 | 75篇 |
1994年 | 65篇 |
1993年 | 44篇 |
1992年 | 35篇 |
1991年 | 46篇 |
1990年 | 41篇 |
1989年 | 26篇 |
1988年 | 22篇 |
1987年 | 18篇 |
1986年 | 14篇 |
1985年 | 13篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1964年 | 1篇 |
1959年 | 1篇 |
1957年 | 2篇 |
1936年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
In this paper, we are interested in the regularity estimates of the nonnegative viscosity super solution of the $β$−biased infinity Laplacian equation $$∆^β_∞u = 0,$$ where $β ∈ \mathbb{R}$ is a fixed constant and $∆^β_∞u := ∆^N_∞u + β|Du|,$ which arises from the random game named biased tug-of-war. By studying directly the $β$−biased infinity Laplacian equation, we construct the appropriate exponential cones as barrier functions to establish a key estimate. Based on this estimate, we obtain the Harnack inequality, Hopf boundary point lemma, Lipschitz estimate and the Liouville property etc. 相似文献
52.
53.
On the isomorphisms and automorphism groups of circulants 总被引:2,自引:0,他引:2
Denote byC
n(S) the circulant graph (or digraph). LetM be a minimal generating element subset ofZ
n, the cyclic group of integers modulon, and
In this paper, we discuss the problems about the automorphism group and isomorphisms ofC
n(S). When M
S
, we determine the automorphism group ofC
n(S) and prove that for any T
if and only ifT = S, where is an integer relatively prime ton. The automorphism groups and isomorphisms of some other types of circulant graphs (or digraphs) are also considered. In the last section of this paper, we give a relation between the isomorphisms and the automorphism groups of circulants. 相似文献
54.
55.
伏安型植物组织生物微电极的研究:混合不同植物组织碳糊微电极的研究 总被引:3,自引:0,他引:3
由于香蕉组织中含有的氧化酶能够生物催化氧化多巴胺,去甲肾上腺素,L-多巴等,大大地提高了植物组织电极的灵敏度;又由于茄子组织中所含有的氧化酶在催化氧化儿茶酚的同时,能有效地抑制抗坏血酸在电极上的反应,将上述两种植物组织混合制成电极,使其更适于神经递质的测定,线性范围:2.4×10^-6--9.8×10^-4mol/L;检出下限3.2×10^-7mol/L。 相似文献
56.
57.
Meng M Stievano L Lambert JF 《Langmuir : the ACS journal of surfaces and colloids》2004,20(3):914-923
Glycine was adsorbed on the surface of a well-defined silica from aqueous solutions of variable concentrations and pHs. The adsorbed molecules were characterized using middle-IR and UV-vis-NIR spectroscopies. Except at the lowest pH (2.0), they were predominantly present on the surface as zwitterions. Two successive deposition mechanisms were evidenced with increasing glycine concentration. At low concentrations, glycine is specifically adsorbed on silica surface sites, probably through its NH3+ moiety. The pH dependence suggests that these sites may be silanolate groups (approximately equal to Si-O-). At higher concentrations, specific adsorption sites are saturated and surface-induced precipitation of beta-glycine is observed. The thermal reactivity of adsorbed/deposited glycine was then investigated by thermogravimetric analysis, in situ diffuse reflectance IR spectroscopy, and thermoprogrammed desorption coupled with mass spectrometry. Adsorbed glycine molecules react to form peptide bonds at a temperature considerably lower than that for bulk crystalline alpha-glycine. The main reaction product is the cyclic dimer diketopiperazine, with no evidence of the linear dimer. The activation mechanism is not diffusionally limited; the formation of "surface acyls", previously proposed for related systems, has not been evidenced here. These findings are of relevance for the evaluation of prebiotic peptide synthesis scenarios. 相似文献
58.
讨论了铀同位素标准物质(UIRM)研制中的一些技术问题,如IRM中同位素丰度的定值,IRM不确定度的影响因素等,并介绍了国内外UIRM研制情况。 相似文献
59.
Lin Jiacheng Li Qianqian Zeng Xiaodong Chen Ziyang Ding Qihang Li Yang Zhou Hui Meng Xianli Chen Deliang Deng Zixin Hong Xuechuan Xiao Yuling 《中国科学:化学(英文版)》2020,63(6):766-770
Osteosarcoma is the most common primary malignant tumor of bone, particularly among children and adolescents. Advances in imaging, surgical techniques, and implants have dramatically reduced the need for amputation in the past three decades.Recently, in vivo fluorescence imaging in the second near-infrared window(NIR-II, 1,000–1,700 nm) shows impressive advantages of deeper tissue penetration and higher spatial resolution, which makes it a promising tool for the early diagnosis and post-operative observation of Osteosarcoma. To the best of our knowledge, this paper is the first time to develop a novel NIR-II fluorescence probe conjugated with an osteosarcoma targeted oligopeptide for molecular tumor imaging in a xenograft orthotopic osteosarcoma mouse model. 相似文献
60.